function Map(ele){
    //1.保存下地图对象
    this.ele=ele
    //2.记录地图相关属性
    this.width=800
    this.height=400
}

Map.prototype.create=function(){
    //设置div宽高背景边框
    //this代表map构造函数中的属性
    this.ele.style.width=this.width+'px'
    this.ele.style.height=this.height+'px'
    this.ele.style.background='url(./bg.png)'
    this.ele.style.border='10px solid green'
    this.ele.style.position='relative'
}